<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
<form id="form">
    用户名：<input type="text" name="name"><br>
    密码：<input type="text" name="password"><br>
    <button id="btn">提交</button>
</form> 
<script>
    const form = document.getElementById("form")
    const btn = document.getElementById("btn")
    btn.onclick = function (e){
        e.preventDefault()
        const xhr = new XMLHttpRequest()
        const formdata = new FormData(form)
        xhr.open("post","http://localhost:5000/test")        
        xhr.send(formdata)
    }
</script>   
</body>
</html>